1. Technical Field
This invention relates in general to user interfaces and, more particularly, to a visual projection device.
2. Description of Prior Art
Many electronic devices require a visual user interface. Examples of devices which require a visual user interface include, but are not limited to, computers, electronic video games, and televisions. The most prevalent visual user interface is the cathode ray tube (CRT), which creates an image by illuminating phosphors on a screen. Another common visual interface device is the liquid crystal display (LCD) which is used in portable electronics, such as notebook computers and hand-held televisions.
While providing a clear picture, cathode ray tubes have several shortcomings. First, the size of a display using cathode ray tube technology is extremely bulky. Even fairly small displays (12" or 14" diagonal) are far too bulky for portability. Second, the cost of a CRT increases dramatically as the size of the screen is increased. Third, the flyback transformer used in a CRT generates a significant magnetic field, which some believe may cause medical problems.
LCD screens have similar disadvantages. First, the clarity of an LCD screen is inferior to a CRT, and it may diminish significantly from the optimum if lighting conditions are not perfect. Second, the cost of the screen increases significantly with size. Screens of medium size, such as 17" screens, are not commercially available.
More significantly, both screens result in eye fatigue after use over extended periods of time. One cause of eye fatigue is the user's constant focus on a screen which is a set distance from the user's eyes. Such constant focus can result not only in eye weariness, but also in headaches and tension. To combat fatigue, many users take frequent breaks; however, this results in a loss of productivity.
Another problem is use of the screen to output three dimensional (3D) information. One method to output 3D information from a CRT or LCD uses special glasses which are synchronized to the output on the screen. The right and left eye pieces of the glasses are alternately blocked, inhibiting the user's vision of the screen by the blocked eye. By outputting a picture at a first perspective when the right eye is blocked and the same picture at a slightly different perspective when the left eye is blocked, a 3D image is received by the user. However, the special glasses are expensive and uncomfortable to wear for extended periods of time.
Yet another problem with prior art displays is the ability for other people to see the output of the display. In many situations, such as during use of a portable computer in an airport terminal, it is desirable for the output of the computer to be private to the user. Even in office settings, it may be desirable to restrict viewing of the output of a computer to the user. While some present day LCD displays have a limited range of viewing, they can still be seen by people substantially behind the user.
Therefore, a need has arisen for a display system for providing a high quality image to the user while decreasing eye fatigue.